Library for talking to APA102 "DotStar" RGB LED strips via SPI

apa102.py

"""
Library for talking to APA102 "DotStar" RGB LED strips via SPI
Requires external package spidev

Developed by Branden Hall (bhall@automatastudios.com)
"""
import math
import spidev


class APA102():

    def __init__(self, bus, device, speed, num_leds):
        """
        Initialize an LED strip

        5000000 (5mHz) seems to work well on RPi2 for speed
        """
        self.bus = bus
        self.device = device
        self.speed = speed

        self.spi = spidev.SpiDev()
        self.spi.open(self.bus, self.device)
        self.spi.max_speed_hz = self.speed

        self.num_leds = num_leds
        self.header = [0, 0, 0, 0]
        self.footer = [0, ] * int(math.ceil(self.num_leds / 16.0))
        self.clear_state = self.header + [255, 0, 0, 0] * self.num_leds + self.footer
        self.clear()

    def clear(self):
        """ Clear the strip """

        self.data = self.clear_state[:]

    def darken(self):
        """ Darken the strip - good for fading out """

        for i in range(self.num_leds):
            index = 4 * (i + 1)
            self.data[index + 1] >>= 1
            self.data[index + 2] >>= 1
            self.data[index + 3] >>= 1

    def close(self):
        """ Set all pixels to black and close hardware connection """

        self.clear()
        self.update()
        self.spi.close()

    def show_color(self, color):
        """
        Set all pixes to specified color

        color - tuple in (r, g, b) format
        """

        self.data = self.header + [255, color[2], color[1], color[0]] * self.num_leds + self.footer

    def add_color(self, pixel, color):
        """ Add color to the specified pixel """

        index = 4 * (pixel + 1)
        self.data[index + 1] += min(255, color[2])
        self.data[index + 2] += min(255, color[1])
        self.data[index + 3] += min(255, color[0])

    def get_pixel(self, pixel):
        """ Get the color at the specified pixel """

        if pixel > -1 and pixel < self.num_leds:
            index = 4 * (pixel + 1)
            return (self.data[index + 3], self.data[index + 2], self.data[index + 1])
        else:
            return None

    def set_pixel(self, pixel, color):
        """ Set the color at the specified pixel """

        if pixel > -1 and pixel < self.num_leds:
            index = 4 * (pixel + 1)
            self.data[index + 1] = color[2]
            self.data[index + 2] = color[1]
            self.data[index + 3] = color[0]

    def update(self):
        """ Update the LEDs """

        try:
            self.spi.writebytes(self.data)
        except:
            self.spi.close()
            self.spi = spidev.SpiDev()
            self.spi.open(self.bus, self.device)
            self.spi.max_speed_hz = self.speed